"Bai" refers to Bai Juyi, a realistic poet, "Su" refers to Su Dongpo, a representative figure of the wild poets, and "Yun" refers to the elegant prose. He is the originator of "Huajian School", and the scenes described in his poems are full of tenderness, which often makes people feel warm like spring breeze. But they are referring to Meng Haoran, whose poems are natural and simple, fresh and extraordinary, rich in meaning and full of charm.
Downstairs, plain and vulgar are all from Su Shi, which is very suitable.